Interests and thoughts from the world of audio and acoustics…

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I saw an article this week about the Royal Festival Hall Organ, which has been refurbished and has returned to the hall after 9 years; now that’s a long refurbishment! It was an interesting article about the history of the organ and why it was being refurbished; however, as I was reading one sentence caught my attention as it seemed a slightly odd thing to point out… It read as follows:

And at full tilt, it makes the very air shake, leaving you feeling as if your molecular structure has been re-ordered.

This made me smile somewhat, as the writer of this article clearly didn’t quite grasp the concept of how sound travels, or how an organ works. “At full tilt”? Air vibrates at any volume you play the organ at, thats how sound travels in an organ, or in any other aspect of life!

Organs are made up of many pipes, which work on the basis of sound vibrating in them, like when you have a bottle and you blow over it and it makes a tone. The many size pipes resonate (the air inside them vibrates) at different frequencies, like when you then fill your bottle with some water and blow over it again. The sound from each pipe is called a pure tone as it does is not altered once inside the pipe, however, when these many pure tones are played together, they create different tones.

Organs are unique in the instrument world, as they have the ability to sound like other (classical) instruments, e.g. brass or woodwind, by combining different combinations of pipes; when all pipes are combined, you get a classic organ sound, which would be similar to a whole orchestra playing the same note all at once. There are often many switches and buttons on an organ, which open and close pipes, meaning the different instrument sounds can be played.

This process of adding several pure tones together in order to imitate other instruments is not uncommon however, as it is the same theory that your electric keyboard or synthesiser is based on. In synthesis, sine waves (the most simple sound wave) are added together with some clever maths discovered by a guy called Fourier, which makes them into instrument sounds. This means that the more money you spend on an electric keyboard, the better it will sound because more sine waves have been used to give greater detail for each note.

So next time you are playing your keyboard, thank the organ for the sound you can hear! And if that isn’t enough for you, then have a look at this interesting take on an organ. Let me know what you think!